1. Field of the Invention
The invention relates to refrigeration systems employing refrigerant cooled compressor motors wherein liquid refrigerant is introduced into the rotor-stator gap of the motor casing thus providing cooling of the motor. More particularly, the invention pertains to a motor cooling system having a high pressure selector valve to regulate the liquid refrigerant flow to the motor casing.
2. Description of the Prior Art
An air conditioning system of the type under consideration includes a motor driven multistage compressor, an evaporator, a first condenser connected to the first stage of the compressor, and a second heating condenser connected to a subsequent compressor stage. These arrangements are employed in air conditioning systems to provide simultaneously cooling to one portion of a building and heating to another portion of the building. If the system is required to satisfy a cooling load, the vapor refrigerant discharged from the first compressor stage is passed to the first condenser wherein it is converted to a liquid and is then passed to an evaporator or cooler. If the system requires heating, the vapor refrigerant discharged from the second stage of the compressor is passed to a second condenser which serves as a heat exchanger and rejects heat to a coolant. An impeller for the compressor is rotated by the electric motor and liquid refrigerant from the refrigeration system is used as the cooling medium for the motor. High pressure refrigerant liquid from the condenser is introduced into the casing of the motor where it absorbs heat from the motor components.
In the above-described installations there are conditions when the cooling load drastically decreases but heating demand is high. In this situation the cooling condenser will not reject the heat and no, or little, refrigerant will be condensed in the first condenser. At this time all the refrigerant will be fed into the second stage of the compressor and directed to the heating condenser. In these conditions no liquid refrigerant is available from the first condenser to maintain the required cooling refrigerant flow to the motor. Therefore, the motor cooling refrigerant must be supplied from the second or heating condenser and it must be supplied automatically.